BAEKJOON 2468

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;

public class Main {
	static int N, cnt, max = Integer.MIN_VALUE, ans;
	static int[][] map;
	static boolean[][] visit;
	static int[] dy = { -1, 1, 0, 0 }, dx = { 0, 0, -1, 1 };

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		N = Integer.parseInt(br.readLine());
		map = new int[N][N];
		
		for (int i = 0; i < N; i++) {
			StringTokenizer st = new StringTokenizer(br.readLine());
			for (int j = 0; j < N; j++) {
				map[i][j] = Integer.parseInt(st.nextToken());
				max = Math.max(map[i][j], max);
			}
		}
		for (int k = 0; k < max; k++) {
			visit = new boolean[N][N];
			cnt = 0;
			for (int i = 0; i < N; i++) {
				for (int j = 0; j < N; j++) {
					if (map[i][j] > k && !visit[i][j]) {
						bfs(i, j, k);
						cnt++;
					}
				}
			}
			ans = Math.max(ans, cnt);
		}
		System.out.println(ans);
	}

	private static void bfs(int y, int x, int d) {
		Queue<Node> q = new LinkedList<>();
		q.offer(new Node(y, x));
		visit[y][x] = true;
		while (!q.isEmpty()) {
			Node n = q.poll();
			for (int i = 0; i < 4; i++) {
				int ny = n.y + dy[i];
				int nx = n.x + dx[i];
				if (ny < 0 || nx < 0 || ny >= N || nx >= N || visit[ny][nx] || map[ny][nx] <= d)
					continue;
				q.offer(new Node(ny, nx));
				visit[ny][nx] = true;
			}
		}
	}

	static class Node {
		int y, x;

		Node(int y, int x) {
			this.y = y;
			this.x = x;
		}
	}
}